The present disclosure is generally related to image guided medical procedures using a surgical instrument, such as a catheter, a biopsy needle, a fibre optic scope, an optical coherence tomography (OCT) probe, a micro ultrasound transducer, an electronic sensor or stimulator, or an access port based surgery.
In the example of a port-based surgery, a surgeon or robotic surgical system may perform a surgical procedure involving tumor resection in which the residual tumor remaining after is minimized, while also minimizing the trauma to the intact white and grey matter of the brain. In such procedures, trauma may occur, for example, due to contact with the access port, stress to the brain matter, unintentional impact with surgical devices, and/or accidental resection of healthy tissue.
FIG. 1 illustrates the insertion of an access port into a human brain, for providing access to internal brain tissue during a medical procedure. In FIG. 1, access port 12 is inserted into a human brain 10, providing access to internal brain tissue. Access port 12 may include such instruments as catheters, surgical probes, or cylindrical ports such as the NICO BrainPath. Surgical tools and instruments may then be inserted within the lumen of the access port in order to perform surgical, diagnostic or therapeutic procedures, such as resecting tumors as necessary. The present disclosure applies equally well to catheters, DBS needles, a biopsy procedure, and also to biopsies and/or catheters in other medical procedures performed on other parts of the body.
In the example of a port-based surgery, a straight or linear access port 12 is typically guided down a sulci path of the brain. Surgical instruments would then be inserted down the access port 12.
Optical tracking systems, used in the medical procedure, track the position of a part of the instrument that is within line-of-site of the optical tracking camera. Since the tip of the surgical instrument may be inserted within a patient, line of site to the tip of the instrument cannot always be maintained. As well, positioning the optical tracking mechanisms at the tip may be too cumbersome to be of practical use. Conventionally, the tip and orientation of the instrument is inferred through a known transformation (e.g., either measured or determined by manufactured drawings) from the visible tracked position to the tip position.
Surgical instruments are typically rigid in nature. When these rigid tools come into contact with different densities of tissues (i.e., white matter, gray matter, tumors, muscle, etc.), the tips of the instruments may deflect or flex. This flexion may not be accounted for in the determination of the tip and orientation of the instrument since the assumption of rigidity is no longer accurate. For example, in a deep brain stimulation (DBS) or biopsy procedure, a surgical instrument with a diameter of 1-2 mm may be inserted into the brain. As this instrument comes into contact with tissue of different densities and/or stiffness, flexion of the instrument may occur (e.g., the track of the instrument may be diverted causing the tip of the instrument to flex up to 5 mm or more during contact with the tissue), thus resulting in inaccuracies.
Alternately, tracking a tool that has unknown geometry from the tracked portion (e.g., a separate piece clamped onto an existing instrument) requires computer knowledge of the geometry from the tracked instrument to the tip of the tool. Other examples include surgical instruments that allow the user to deform the instruments in an arbitrary way prior to use, such as a NICO Myriad device.
Conventional surgical navigation systems may use electromagnetic (EM) sensors such as fluxgates or induction coils for tracking the tip of surgical instruments. For example, a system such as the Aurora® Electromagnetic Tracking System from Northern Digital utilizes EM sensors. These conventional systems allow for miniature sensors to be placed at the tip of the instrument, thus allowing direct tip tracking. However, these conventional instruments rely on a stable magnetic field to be generated around the tracking volume which is impractical, if not impossible in real-life surgical environments, leading to loss of position accuracy and spurious results. Other surgical instruments have incorporated Bragg Gratings on fiber optics to achieve tip deflection information. Furthermore, it is often not possible to adapt existing surgical instruments so that the tracked portion is at the desired tip of the instrument, for example if the tip delivers energy (such as a cauterizing instrument) which could affect the tracking sensor, or if the tool was manufactured without anticipating a means to allow a tracking sensor at the tip. In these cases it is more generally useful to position the tracked portion away from the tip (e.g., a separate piece clamped onto an existing instrument) and infer the tip position from the tracked position.
In another example, the present disclosure may apply to an articulated arm system where the ex-vivo position of an instrument is determined by measuring the joint angles of the arm. However, the internal tip position would still need to be determined using aspects of the present disclosure. Therefore, there is a need to provide alternate mechanisms to counter flexion in surgical instruments when performing medical procedures.